(63a) Biogas as a Natural Gas Supplement: Consideration of Potential Safety Issues

Biogas is the common moniker for a flammable gas mixture that is formed from the anaerobic digestion of organic matter. Biogas is most often derived from waste streams in agricultural or chemical processing facilities.  Biogas contains methane, but it is not natural gas.  Biogas is used to supplement natural gas as a fuel gas for fired heaters and boilers. The integration of biogas into a natural gas header system is not overly complicated, but there are oftentimes overlooked safety concerns related to component maintenance and equipment performance when performing the integration. Pipeline natural gas is heavily processed before reaching the customer; in contrast, little preparation of biogas is performed before addition to the natural gas infrastructure of a facility. Problems may arise when maintenance and operation protocols are established for pure natural gas operations and the system is modified at a later date to accommodate biogas supplementation. In this paper we discuss the general methods for forming biogas, the expected compositions of biogas, the common methods for integrating biogas into a natural gas supply system, potential impacts biogas may have on typical gas-fired operations, followed by a review of several case studies where biogas supplement systems led to unanticipated issues with flammable gas consuming facilities.